title: An in vivo comparison of hip structure analysis (HSA) with measurements obtained by QCT.
abstract: CONCLUSIONS
  In a population of elderly women, bone cross-sectional area (CSA), cross-sectional moment of inertia (CSMI), section modulus (Z), femoral neck axis length (FNAL), and width measured with hip structure analysis (HSA) on dual-energy x-ray absorptiometry (DXA) images in the femoral neck and trochanteric regions are highly correlated to quantitative computed tomography (QCT) measurements.
  
  
  BACKGROUND
  HSA is a method of obtaining measurements of proximal femur structure using 2D DXA technology. This study was designed to examine the correlations between HSA measurements and 3D QCT.
  
  
  METHODS
  Forty-one women (mean age, 82.8 ± 2.5 years) were measured using DXA and a 64-slice CT scanner (1 mm slice thickness, 0.29 mm in plane resolution). HSA parameters were calculated at the narrow neck (NN) and trochanteric (IT) regions on the DXA image. These regions were then translated to anatomically equivalent regions on the QCT dataset by co-registering the DXA image and QCT dataset using four DXA images acquired at different angles.
  
  
  RESULTS
  At the NN and IT regions, high linear correlations were measured between HSA and QCT for CSA r = 0.95 and 0.93, CSMI r = 0.94 and 0.93, and Z r = 0.93 and 0.89, respectively. All correlations were highly significant (p < 0.001), but there were differences in slope and offset between the two techniques, at least in part due to differences in calibration between the two techniques. FNAL and width of the bone at the NN and IT regions, physical measurements independent of the calibration, were highly correlated (r = 0.90-0.95, p < 0.001) and had slopes close to 1.0 (range, 0.978 to 1.003).
  
  
  CONCLUSIONS
  CSA, CSMI, Z, FNAL, and width measured by HSA correlate highly to high-resolution QCT.
authors.affiliation: Skeletal Health, Hologic, Inc., Bedford, MA, USA.
authors.forename: K
authors.initials: K
authors.lastname: Ramamurthi
authors.forename: O
authors.initials: O
authors.lastname: Ahmad
authors.forename: K
authors.initials: K
authors.lastname: Engelke
authors.forename: R H
authors.initials: RH
authors.lastname: Taylor
authors.forename: K
authors.initials: K
authors.lastname: Zhu
authors.forename: S
authors.initials: S
authors.lastname: Gustafsson
authors.forename: R L
authors.initials: RL
authors.lastname: Prince
authors.forename: K E
authors.initials: KE
authors.lastname: Wilson
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D005272:Femur Neck / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D006621:Hip Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods